The recent technique of implantation sites comprises a local anesthesia procedures wherein an injection chamber is placed below the subcutaneous tissue in such a manner that this chamber is accessible through the skin; this chamber is connected to a catheter which feeds the substance directly to the applicable area of the body. These injection sites may remain over a long time within the body of the patient and make it possible to eliminate repeated intravenous, intra-arterial, intra-rachidic, cerebral intraventricular or intraperitoneal injections and to replace them by simple subcutaneous injections.
A first type and presently commercially available device injects each time one dose of therapeutant (hereafter denoted by "embolus"). These devices include a rigid disk, especially one made of stainless steel over which there is an elastic silicone membrane acting as a deforming cone; the injection chamber a volume inside of this dome and communicates with a catheter. During the implantation, the dome is directed toward the skin line so as to be accessible on one hand to an injection needle and on the other hand manually through the skin.
Following implantation, this type of device is made operative by passing a needle mounted on a syringe through the membrane in order to feed the therapeutant to the inside of the deforming dome constituting the chamber (the metal disk sealing the chamber acting as a stop against the tip of the needle), and thereupon, after the needle has been withdrawn, the elastic dome is manually pressed through the skin in order to expel the therapeutant dose toward the catheter.
However devices of that kind incur several drawbacks. In the first place, they only allow injecting emboli by units and are inappropriate for long-term perfusions. This is so because the elastic dome of the device is unfit to keep stably in place a perfusion needle. Further, these devices have a relatively short service life because after several hundred injections, the elastic dome becomes the seat of micro-infiltrations: thereupon the device must be changed, and surgical intervention again is required. Also, such devices suffer from the major drawback that the embolus in the injection chamber formed by the deforming dome is never wholly expelled into the catheter when the operator manually presses on the dome no matter how much care is being expended; the variable slight amount of residual therapeutant in the dome after the pressure was exerted degrades the accuracy of the injected dose and in some treatments that may be highly prejudicial, especially when administering such active ingredients as opiates neuro-mediators, antimitotics, which require accurate dosage.
Another type of known device makes possible perfusion but lacks any manually actuated membranes for injecting emboli. These latter devices comprise a cylindrical chamber made of stainless steel which is closed on one side by a stainless steel bottom and on the other by a septum allowing to impermeably pass the perfusion needle. The essential drawback of these devices is that their usefulness is restricted to perfusion because they do not allow unit-feeding emboli corresponding to an accurate and predetermined amount of therapeutant; now there is presently such a need in very many therapeutic treatments (long-term chemotherapy, pain treatment by epidural or intrathecal morphine injections . . . ). Furthermore, the geometry of these devices requires a perpendicular puncture whereby practical difficulties are encountered to keep the needle in place during perfusion and in connecting it to the external supply system. Moreover, these devices also suffer from the disadvantage that they are fairly expensive and that their bulk is substantially larger than the flexible-dome devices (especially in height), whereby implantation is more difficult and causes a boss underneath the skin that might bother the patient.
The object of the present invention is to provide an improved device allowing universal application both for embolus injections and for extended perfusions.
Another main object of the invention is to provide a device capable of supplying an exact and predetermined dose of therapeutant in an injection.
Another object of the invention is to provide a device of much longer service life than the elastic-dome devices.
Another object is to provide an economical and compact device lending itself to easy implantation in the subcutaneous zone.
Another object is to provide a device entailing no risk at all of artifacts or interferences in exploration by modern imaging means (tomodensitometry, magnetic resonance . . . ).